Search results for " Extraction"
showing 10 items of 1344 documents
Extraction of dansylated amino acids using the supported liquid membrane technique
1997
Extraction using the supported liquid membrane (SLM) technique demands conditions where the extracted compounds can be made uncharged allowing them to pass through the membrane. For amino acids, being bifunctional, such conditions can not be obtained directly. One way to overcome this problem is to block one of the functionalities by derivatization, utilising the other group for the transport. The SLM extraction of dansylated amino acids was investigated and optimized. It was possible to obtain high extraction efficiencies (>90%) for most amino acids. For amino acids with polar side chains, such high extraction efficiencies were only obtained at low analyte concentrations ( 10 nmol 1-l). Fo…
Electrochemically triggered iodide-vacancy BiOI film for selective extraction of iodide ion from aqueous solutions
2021
Abstract The effective extraction and regeneration of radioactive iodide remains an urgent concern for safe nuclear energy utilization. Herein, we developed a novel electrochemically triggered iodide-vacancy BiOI film, which exhibited excellent I− ion extraction capacity of 328.3 mg·g−1. Especially, due to the ion vacancy trap effect, the film showed high selectivity towards I− ions in the existence of a large number of competitive anions. Additionally, the electrochemically switched ion extraction (ESIE) process with this iodide-vacancy BiOI film possessed fast extraction kinetics and high stability. More importantly, the trapped I− ions were easily desorbed from the film without the secon…
Influence of dissolved humic material and ionic strength on C8 extraction of pesticides from water
1995
A mixture of twelve intermediate polarity pesticides, mostly carbamate-type, have been chromatographied on an octadecyl-silica bonded-phase column using acetonitrile-water gradient mobile phase and UV detection. Pesticides were extracted from aqueous matrix by solid-phase extraction. The extraction system consisted of a glass microcolumn containing octyl-silica solidphase conditioned with methanol and water. The elution was by acetonitrile-dichloromethane (50:50). Studies of extraction factors like volume of sample, addition of 10% sodium chloride and presence of dissolved humic material are investigated.
Water-soluble polysaccharides from Opuntia stricta Haw. fruit peels: Recovery, identification and evaluation of their antioxidant activities
2015
Abstract Opuntia stricta Haw. is considered as one of the most common cactus plant growing in Tunisia. Extracting valuable compounds from its fruit peel, considered as by-product, is drawing more and more attention, making it on the verge of commercialization. Water-soluble polysaccharides were extracted from Opuntia stricta Haw. peels, and their chemical composition assessed using thin layer chromatography. The antioxidant activities of the extracted polysaccharides were assessed using 2,2-diphenyl-1-picrylhydrazyl free radical scavenging activity, total antioxidant activity and reducing power capacity. The extraction yield of water-soluble polysaccharides was 7.53±0.86%. The chemical comp…
Application of Molecular Imprinted Polymers for Selective Solid Phase Extraction of Bisphenol A
2016
Abstract Selective molecularly imprinted polymers (MIPs) with bisphenol A as template were synthesized using the non-covalent imprinting approach. MIPs were prepared using thermally initiated polymerization with 1,1’-azobis(cyclohexanecarbonitryle) (ACHN) as initiator and ethylene glycol dimethacrylate (EDMA) as a cross-linking agent. The tested functional monomers included methacrylic acid, acrylamide, and 4-vinylpyridine. The selectivity of the BPA-MIP for the solid phase extraction of bisphenol A was tested in samples containing other related alkylphenols. The polymers prepared in acetonitrile using methacrylic acid or acrylamide as monomer showed the highest selectivity towards target a…
Analysis of carbamate pesticides and their metabolites in water by solid phase extraction and liquid chromatography: A review
2001
Carbamates are an important, broad class of pesticides that are used extensively as insecticides, fungicides, and herbicides. Sensitive, economical, fast, and environmental friendly procedures are constantly developed to investigate their residues in water samples. The state of the art in methods based on solid phase extraction (SPE) and liquid chromatographic determination are examined here. SPE is presently the most extended method for preconcentration of carbamate pesticide residues and their transformation products from water samples. Advantages and limitations of alkyl bonded-silica, and polymeric sorbents, carbon, and mixed-phases in off-line and on-line procedures are discussed. Beca…
Solid–liquid extraction of ω-amino acids using ditopic receptors
2008
Abstract Five heteroditopic ligands have been prepared to be used in solid–liquid extraction of ω-amino acids into DMSO solutions. The prepared ligands contain crown ethers as cation binding sites and thiourea or amide groups for anion recognition. The aliphatic zone of the 1H NMR spectra suggests that two different species related to the amino acid are present in solution. One of these species is the complexed zwitterionic form and the other seems to be free non-zwitterionic amino acid. The presence of these two species allows extraction efficiencies higher than 100%.
Influence of the presence of surfactants and humic acid in waters on the indophenol-type reaction method for ammonium determination.
2005
Abstract This work has evaluated the influence of humic acid and/or surfactants in the quantification of ammonium in waters with the indophenol-type reaction method. Thymol has been employed with the colorimetric method for sample ammonium concentrations between 0.25 and 1 mg L −1 . In addition, SPE/diffuse reflectance method has been used for quantification of ammonium at low concentrations (between 0.025 and 0.25 mg L −1 ). Matrix effect owing to humic substances were observed with the colorimetric method when the concentration was equal or higher than 25 mg L −1 . Lower concentrations of humic compounds produced matrix effects with the more sensitive SPE/diffuse reflectance method. Gener…
Sensory and Chemical Analysis of Fractions Obtained by Gel Permeation of Water-Soluble Comte Cheese Extracts
1995
The pure water extraction of Comte cheese solubles and their chromatographic separation facilitate sensory analysis experiments with the fractions directly collected from the column. Two extracts, one obtained after ultrafiltration, the other after chromatography on Sephadex G25, have been separated on Toyopearl HW-40S. The sensory evaluation of the obtained fractions shows in the two cases that some fractions have interesting flavors. However, physicochemical analysis shows that organoleptic characteristics are linked more to the presence of amino acids and salts than to the presence of peptides. Apart from monosodium glutamate, most of the amino acids are present in the fractions at conce…
Selective extraction of small proteins from biological samples using a novel restricted access column with cation exchange properties
2000
The determination of proteins utilising a polymer-based restricted access suppor material with ion exchange properties (IERAM) is outlined. Solid phase extraction coupled on-line with a mincrobore reversed phase HPLC system for the quantitation of small marker proteins is demonstrated. The cation-exchange restricted access packings were characterised with respect to their adsorption and desorption kinetics. The IERAM material was also investigated by capacity, selectivity, and biocompatibility determinations when applied to the quantification of small molecular weight proteins such as cytochrome C, Lysozyme, Ribonuclease A, Myoglobin, Insulin, human serum albumin, and a Tryptic inhibitor.